Pharmacy Maths Equations! :(

Question 1

In eye drops, how many drops in 1 mL?

Answer 1

20 drops in 1 mL

Question 2

What is the BMI equation?

Answer 2

Weight (Kg) / Height (m2)

Question 3

What is the equation for ARR?

Answer 3

Absolute risk reduction = control rate - experimental rate

RRR = control rate - experimental, then ANS / control rate

Question 4

How do you calculate the NNT?

Answer 4

Number Needed to Treat = 100 / (ARR%)

Question 5

How do you calculate the amount of suppository base?

Answer 5

(S x M) - (Total quantity of Drug A (g) (number of suppositories x weight (g)) / DV)

S = number of suppositories
M = mould capacity of the suppositories => 4g is adult; 2g is child; and 1g is infant

Question 6

Regarding displacement values, what 3 things do you need to calculate for them?

Answer 6

1. Total DV of the drug
2. Total VOLUME of the final drug solution
3. Total WEIGHT of the drug

You’ll need 2/3 of these things to figure out the problem!

Question 7

How do you convert from hours to minutes?

Answer 7

1h = 60mins, thus, 1min is achieved by dividing by 60.

Question 8

What does 1350PPM stand for?

Answer 8

1350g in 1,000,000g
Number of parts in 1 million parts.

Question 9

Chemistry based equations

Answer 9

GRAMS (g) = MR (g/mol) X MOL (mol)
MOL (mmol) = CONC (mmol/mL) x vol (mL)

Question 10

How to calculate the DF (Dilution Factor)?

Answer 10

DF = Vol of final solution (mL) / Vol of stock solution (mL)

Question 11

How do you work out the anhydrous drug?

Answer 11

Anhydrous = without water
Hydrous = with water

If 20% was moisture then, 100% - 20% = 80% is ANHYDROUS drug

Question 12

What’s the difference between CrCL and eGFR?
(https://pediaa.com/what-is-the-difference-between-gfr-and-crcl/)

Answer 12

CrCL is a direct measurement in the importance of estimating the eGFR, whereas the eGFR is an indirect measurement which is important for the diagnosis, prognosis, and treatment of kidney disease.

Question 13

What are the CrCL values for the levels of renal impairment?

Answer 13

x < 10mL/min => SEVERE
10 - 20mL/min => MODERATE
x < 50mL and x > 20mL = MILD

• Cockcroft and Gault is the preferred method for estimating renal function in elderly patients over 75 years OR at extremes of muscle mass. For example, reduce muscle mass will lead to overestimation of GFR and increased muscle mass will lead to underestimation of the GFR.
• IBW should be used in the equation.
• This is for patients less than 18kg/m2 or greater than 40kg/m2

Question 14

Double dilutions equation!

Answer 14

Usually if ALL 4 of the C1V1=C2V2 are there, then use this equation:

(C1V1) + (C2V2) / (V1 + V2) = percentage strength of the solution in (V1+V2)mL

Distilled H20 = 0%
“PURE” = 100%

Question 15

1 in 3 Parts

Answer 15

3 parts overall

Question 16

1 to 3 Parts

Answer 16

4 parts overall

Question 17

How many pounds are in 1 stone?

Answer 17

1 stone = 14 pounds

Question 18

How many pounds are in 1 Kg?

Answer 18

1 Kg = ~2.2 pounds

Question 19

Bioavailability

Answer 19

IV = 100% bioavailability
PO = <100% always

E.g.
If a 100mg drug has a bioavailability of 10%, that means 90% of the drug is broken down before it enters the systemic blood supply. Thus, 10mg only makes it through. 10mg is also the equivalent of the IV dose.

PO => IV = x 0.1
IV => PO = divide 0.1

Question 20

Volume of Distribution

Answer 20

Mass (amount of drug in the body) (g) = Density (conc of plasma) (g/L) X Volume (of distribution) (L)

Vd tells us how extensively drug is distributed to the rest of the body compared to the plasma.